Tried interfacing with pi.
Latency is just too high, and jitter is pretty bad too. This will probably only work if input is buffered or parallel out is used (which eats up pins).
EDIT: Latency was my bug. Jitter is fairly high but not high enough to really affect things, about .5uS, except I think it spikes sometimes... The other problem I think is unreliable detection of the clock pulse and latch, each is about 1uS, which may be fixed by stretching the period but I'm not so sure.
Right now the Pi is holding down A and Right. This is what it should look like.
It screws up regularly.
Sometimes it doesn't even bother. I think it didn't see the latch so it didn't get set up correctly though.
Sometimes it misses a pulse, which is what I think the problem really is. Here it misses one somewhere in the middle.
And one right at the beginning, pressing both A and B...
Ultimately with how it is acting I do not think the Pi is a reasonable platform as a playback device. It can probably feed a buffer but it can't respond directly to the NES. I will have to try stretching the clock low and latch high (looks like about 1us right now) to see if it picks up better, but with it sometimes completely missing, I don't know if it could ever work right.